There are presently available lever operated riveters of the type shown in my U.S. Pat. No. 4,520,648 granted June 4, 1985, wherein a blind rivet is set by squeezing a pair of handles on the tool to pull the stem or shank of the rivet through a predetermined stroke, which is sufficient to tightly clamp overlapped work pieces and then sever the stem from the set rivet. While such mechanical riveters are very effective in setting blind rivets that are relatively low in tensile strength, such as plastic rivets, the linkages of such mechanical tool sometimes do not provide sufficient mechanical advantage to set and sever a rivet of relatively high tensile stength.